Spark screen



Oct. 27, 1936. JOHNSON 2,058,694

SPARK SCREEN Filed May 27, 1955 2 Sheets-Sheet 1 [nae/750C John A. Johnson.

Oct. 27, 1936. J, A, JCHN N 4 2,058,694

SPARK SCREEN Filed May 27,1935 2 Sheets-Sheet five/2Z0: Jo/m A Job/250m 7mm m Atomega Patented Oct. 27, 1936 UNITED STATES SPARK SCREEN John A. Johnson, Crawfordsville, Ind., assignor to National Supply & Service Corporation, Crawfordsville, Ind.

Application May 27,

7 Claims.

Reference is made to my United States Patent No. 2,010,862, issued. August 13, 1935, of which this application is a continuation in part.

This invention relates to the art of spark screens to be placed over the discharge ends of fiues or chimneys and the like and has for its primary object the prevention of fires, particularly roof fires, normally caused by burning matter escaping from the flues or chimneys.

It is an important object of the invention not only to arrest burning particles issuing from the flue or chimney but to break up these larger particles or retain them until they have been consumed and at the same time maintain a normal flue or chimney draft under all weather and wind conditions. 7

A still further important objectof my invention is to provide means incorporated in the wall of the screen which will retain under high wind con- "-dit'ions all of the hazardous sized particles issuing from the flue or chimney, in which case, under the highwinds, these particles are of a reduced size and at'the same time have such means as'tov permit the escape 'of larger sized particles from the screen under lighter winds.

A still further important object of my invention is :to provide a total eiiective outlet opening sufficient to retain the normal fiue or chimney draft regardless of the filling up of the spark screen walls with soot or other escaping particles.

These and many other objects and advantages will become apparent to those versed in the art in the following description of my invention as illustrated in the accompanying drawings, in

Fig. 1 is a top plan view of astructure embody- Fig.2, a side elevation; Fig. 3, a transverse horizontal section on the line"3-3 in Fig.2;

Fig. 4. a transverse horizontal section on the line '4-4 in "Fig.2, and

' base left open, the receptacle being herein shown in the one particular form as rectangular in shape and being made-from woven wire.

It is to be particularly noted that in the side ;walls' of the receptacle, hereinafter designated a spark screen, that the lower portion of the side wallsis formed to have openings smaller in size than are the openings in the portions of the walls 1935, Serial No. 23,688

immediately thereabove. These smaller openings I continue from the bottom of the wall in each case upwardly a distance, roughly approximating, about a third of the total height of the screen.

A transverse foraminous floor or partition I I is fixed in the screen preferably at that elevation which is at the top of the smaller holes In so that the larger holes l2 start and continue from above the floor l I. The elevation of the floor may vary somewhat in relation to the plane between'lo the holes of different sizes. This floor II is provided with a major central opening l3 and the holes or perforations in the remainder of the floor H are of greater size than are the holes or perforations l2 in that part of the screen walls above the fioor.

A perforated or foraminous hood or baffle I5 is carried within the spark screen at a distance above the floor ll, roughly approximating a third of the screen wall height thereabove, if anything the spacing being somewhat in excess of this proportion. This baffle I5 is preferably formed in the nature of an inverted dish so as to have a downwardly and outwardly sloping marginal flange Hi. The dimensions of the bafile are such that the outer lower edge of this flange l6 terminates in spaced relation from the walls of the spark screen, the area of the baffle exceeding that of the central opening through the fioor I I.

The baflle I5 is mounted in fixed relation by means of transverse rods or wires l1 passing through the marginal flanges of the baffle l5 and engaging by their ends the transverse wires of the side walls of the spark screen. Clips l8 fix the baflle to the wires ll.

The upper end of the spark screen is turned around inwardly and thence downwardly from the side walls to provide a central opening I9 therethrough which is in a plane below the upper ends of the side walls. The area of the opening is approximately that of the opening it although some variation may be had. The openings or perforations through the baffle 15 and its marginal flange it are substantially the same in size as are the openings l2 in the side wall of the screen.

In the form herein shown, the upper end of the spark screen as above described is formed by bending in the side walls as indicated and then uniting the beveled corners in the bent form by the clips 20, Fig. 1. 50

The variation in size of the openings in the side wall of the spark screen is an extremely im portant feature. When the wind is strongest, the burning matter coming from the chimney is swept almost entirely horizontally across the top155 of the chimney against the lee side of the screen as generally indicated by the lower branch of the arrow A. Winds of lesser velocity will drive the particles along a path indicated somewhat by the upper branch of the arrow A. Therefore, the openings in the wall within that portion of the screen intercepting the path of such wind driven matter are kept small enough to cause all of the dangerous burning particles to be retained within the screen until combustion of such particles has been completed and only those smaller particles are allowed to escape which are harmless and which will have been sufficiently consumed as not likely to cause a roof to become ignited thereby. I find that these openings in the lower portion of the screen wall may have a safe range wherein only spheres from one-fourth to one-half inch diameter may pass through the openings, all larger spheres being retained.

Of course under the high wind conditions, there is more or less of a blast effect on the burning particles which fans the particles and maintains combustion at a higher temperature. When there is little wind prevailing, the burning particles escaping from the chimney will follow some such path as indicated by the arrow B, the particles largely passing through the central opening l3 and over toward the lee side of the screen to pass in part if not entirely through the larger openings I2 in that side wall, the remainder of the particles not going through following the branch part of the arrow within the screen to strike the wall and slide up along its inside and then curve around under the marginal flange at the side of the opening [9, such particles as will complete the travel being carried back again by the wind toward that same lee side as indicated by the curving portion of that branch of the arrow B.

I find that these openings [2, that is, the larger openings above the path of particles taken under high wind condition may be a range in size such as will permit spheres to pass therethrough within the range of from one-half inch to seven-eighths inch and not thereover. It is understood of course, that in any case the openings above the path of those high wind driven particles will be larger. The range of openings is necessary to meet varying conditions encountered by different fuels used in varying parts of the country and also as between domestic and industrial uses. One particular structure which I find to be highly effective particularly in domestic use, has the smaller openings of that size which will just pass a three-eighths inch sphere and the larger openings of that size which will just pass a ninesixteenths inch sphere.

A blast action is set up by the fiue when accumulated soot therein burns out and the screen is particularly effective also in this condition in that the vertically rising particles of burning matter will principally pass through the opening [3 and strike the baffle l5 to be broken up thereby or retained thereunder until consumed. Part of the upwardly rising stream will strike the floor II and be broken up.

While it is of course always desirable to prevent hazardous ignited particles from leaving the screen, it is at the same time necessary to provide a screen of such nature as will not hinder the draft of the chimney under atmospheric conditions wherein the soot, particularly from soft coal, or particles of paper from trash burning tend to fill in or over the openings in the screen. It is for this reason that I maintain the spacing around the bafile l 5 within the wall of the screen and also the clear opening I9 in the top of the screen. The openings through the floor I I are of sufiicient size that in any event they do not tend to become fill-ed with soot or bridged over by snow.

While I have herein shown and described my invention in the best form as now known to me, it is obvious that structural changes may be made without departing from the spirit of the invention and, I, therefore, do not desire to be limited to that precise form beyond the limitations as may be imposed by the following claims.

I claim:

1. A spark screen comprising a foraminous walled receptacle forming a flue extension open from the under side adjacent the flue top and having the lower portion of its side wall, which is subjected to impact by generally horizontally wind driven flue escaping particles provided with openings in size having a range which will just pass spheres from to inch in diameter, and provided with larger openings above said portion in the same said wall in size having a range which will just pass spheres from to inch in diameter.

2. A spark screen comprising a foraminous walled receptacle open from the under side and having the lower portion of its side wall, which is subjected to impact by generally horizontally wind driven flue escaping particles provided with openings in size having a range which will just pass spheres from A; to inch in diameter, and provided with larger openings above said portion in size having a range which will just pass spheres from to inch in diameter, and having a transverse perforate floor located between the smaller and larger side wall openings.

3. A spark screen comprising a foraminous walled receptacle open from the under side and having the lower portion of its side wall, which is subjected to impact by generally horizontally driven fiue escaping particles provided with openings in size having a range which will just pass spheres from A1 to /2 inch in diameter, and provided with larger openings above said portion in size having a range which will just pass spheres a central opening less in area than that of the baffle thereunder.

4. A spark screen comprising a foraminous walled receptacle open from the under side and having the lower portion of its side wall, which is subjected to impact by generally horizontally driven flue escaping particles openings in size having a range which will just pass spheres from A; to inch in diameter, and provided with larger openings above said portion in size having a range which will just pass spheres from to 7 inch in diameter, and having a transverse perforate floor located in the plane between the smaller and larger side wall openings, and a bafile within the upper portion of the receptacle above said floor, the bafiie marginal edge being spaced from the receptacle side walls, said receptacle having its side walls at its top end curved over, around and downwardly to leave a central opening less in area than that of the baflle thereunder, said provided with bafile being perforate with its openings of substantially the same size as those in the upper portion of the receptacle walls.

5. A spark screen comprising a foraminous walled receptacle open from the under side and having the lower portion of its side wall, which is subjected to impact by generally horizontally driven flue escaping particles provided with openings in size having a range which will just pass spheres from A; to inch in diameter, and provided with larger openings above said portion in size having a range which will just pass spheres from to inch in diameter, and having a transverse perforate floor located in the plane between the smaller and larger side wall openings, and a bafiie within the upper portion of the receptacle above said floor, the bafiie marginal edge being spaced from the receptacle side walls, said receptacle having itsside Walls at its top end curved over, around and downwardly to leave a central opening less in area than that of the baffle thereunder, said baffle being perforate With its openings of substantially the same size as those in the upper portion of the receptacle walls, said floor having an opening through its central portion of approximately the area of said central opening through the top of the receptacle.

6. For arresting sparks escaping from a flue under atmospheric conditions varying from no wind to high velocity winds sweeping across the flue opening, a spark arrester positioned about the flue opening and having an upwardly extending foraminous wall, the perforations in the lower portion of the wall adjacent the flue opening being smaller than those in the upper portion, whereby under slight or no wind conditions the sparks coming from the flue opening under influence of the flue draft may strike the I said upper portion and, under higher wind conditions, will principally strike only the said lower, smaller hole portion.

7. For arresting sparks escaping from a flue under atmospheric conditions varying from no wind to high velocity winds sweeping across the flue opening, a spark arrester positioned about the flue opening and having an upwardly extending foraminous Wall, the perforations in the lower portion of the wall adjacent the flue opening being smaller than those in the upper portion, whereby under slight or no wind conditions the sparks coming from the flue opening under influence of the flue draft may strike the said upper portion and, under higher wind conditions, will principally strike only the said lower, smaller hole portion, and a transverse foraminous floor positioned within said arrester on approximately the elevation between the said two portions of said wall.

JOHN A. JOHNSON. 

